Self-obturating, expellable cartridge case

ABSTRACT

A novel cartridge possesses a fin-stabilized, high velocity projectile attached to a propellant casing, which is selfobturating and expelled from the weapon together with the projectile and separated from the latter on muzzle exit. The projectile is located such that its finned end is within the casing and its front end projects beyond the closed front end of the casing which has a ventable closure at its breech end. Sabot means are removably mounted on the projecting part of the projectile such that they abut against the front end of the casing and are thrown off by aerodynamic forces and centrifugal force of low spin generated by engagement of the casing with the rifling.

1 1 tlnrted States atent 1191 1111 3,7500% Wajda et a1. [4 Sept. 1, 119721 SELF-OBTURATING, EXPELLABLE 3,662,686 5 1972 Baldini 102/93 CARTRIDGE CASE 3,665,861 5/1972 Jaslow 102/93 2,389,846 11/1945 Erlcson 102/93 [75] Inventors: Raymond S. Blfljdfl, Pars1ppany;

a Rubin, Sparta, both of FOREIGN PATENTS OR APPLICATIONS NJ. 1,125,503 7/1956 France 102/38 [73] Assignee: The United States of America as represented by the Secretary of the jnmary g gg s Army Washington Dc ttorneyarry aragovl z e a.

[22] Filed: Jill]. 27, 1972 57 ABSTRACT PP 221,233 A novel cartridge possesses a fin-stabilized, high velocity projectile attached to a propellant casing, which is 52 us. CI 102/38, 102/49.4, 102/93, e 9 expelled weapm 102/016 7 w1th the pro ectlle and separated from the latter on s 1 1m. (:1. F42b 5/10 muzzle The Pmjecme mated Such that 58 7 Field of search 102/38, 93, 94, 49.3, fimed end is within the casing and its Pmjws beyond the c1osed front end of the casing whtch has a ventable closure at tts breech end. Sabot means are re- 56 f movably mounted on the projecting part of the projec- 5:25: Zi tile such that they abut against the front end of the eas- ES TS ing and are thrown off by aerodynamic forces and cen- 2 trifugal force of low spin generated by engagement of nspac er et a 3,125,957 3/1964 Lipinski 102/93 x the casmg with the 3,620,167 11/1971 Rorner et a1. 102/93 7 13111111110, 2 Drawing Figures PATENIEB st? 1 ems governmental purposes without the payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to a novel cartridge, adapted for use with high velocity, finstabilized projectiles, wherein the casing is of a self-obturating design and is expelled from the weapon together with the projectile.

Conventional ordnance ammunition consists of a metal casing containing a propellant charge and a projectile, forming a unitary structure or cartridge, which is placed into the breech of a cannon and tired to propel the projectile to the target. The cannon is usually provided with an ejector mechanism for removing the metallic casing after the cartridge has been fired. Conventional cartridges of this type are unsuitable for use in the newest military tank and tank type'vehicles, since ejection of the metallic casings into the vehicle would be intolerable due to space limitations within the vehiale and introduction of toxic gases from the spent cartridges into the vehicle.

Much effort and expense have been spent to overcome this problem. In a design currently used with high-velocity, fin-stabilized projectiles, the cartridge case has been replaced by a non-metallic casing containing highly inflammable nitrocellulose, which is consumed on firing of the propellant charge, thereby eliminating the need for an ejector mechanism and opening of the breech. However, such consumable cartridge cases can be relatively fragile and at present require a cover of rubber or similar elastomeric material to protect them from degradation by water, moisture and oils to minimize handling and operational hazards. Moreover, the current design employs a relatively complex obturating band installation, which must move under the gun pressure to seal the gases behind the projectile.

It is therefore a principal object of this invention to provide a novel cartridge, wherein a fin-stabilized projectile is attached to an expellable, self-obturating propellant casing, thereby eliminating the need for an obturating band on the projectile.

Another object of the invention is to provide a cartridge, wherein a high velocity, fin-stabilized projectile is attached to an expellable, self-obturating cartridge casing, which is capable of withstanding normal handling and protects the propellant against harmful environmental conditions.

Other objects and advantages of the present invention will appear or be obvious from the following detailed description in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION The aforementioned difficulties of the prior art are obviated and the objects of this invention are achieved by a novel cartridge wherein a fin-stabilized projectile is attached to a non-consumable, flexible casing which contains a propellant charge and possesses a closed front end and a ventable closure at its breech end; the finned portion of the projectile is located within the casing and the remaining portion of the projectile projects beyond the front end of the casing; sabot means are removably mounted on the portion of the sub caliber projectile in front of the casing such that they abut against the front end of the casing and are thrown off by the centrifugal and aerodynamic forces; and wherein the gases generated by firing of the propellant charge are vented into the breech area of the weapon, causing the casing to become pressurized and selfobturating and engage the weapon rifling sufficient to impart a low spin, whereby the casing is expelled from the weapon together with the projectile and the latter is separated from the casing and sabot means on muzzle exit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a longitudinal sectional view of a novel cartridge according to the present invention.

FIG. 2 shows a front end view of the cartridge casing illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a cartridge 10 comprising a hollow cylindrical casing 11 of high density polyethylene having the following approximatedimensions: 0D. 5.9 in.; length 25 in.; wall thickness 0.11 in. The breech end of the casing has a base cap 12 of material consumable under the firing conditions, which has a circumferential flange 13 bonded to the end of casing 11 with a suitable adhesive, e.g. an epoxy resin. Base cap 12 possesses a cup 14 containing an initiator for a booster charge of black powder (not shown) and standard stick propellant (not shown) located in the casing. The front end of casing 11 has the shape of a dome, which as shown in FIG. 2 is provided with a center hole 15 which re- 'ceives the sub caliber cylindrical body of the tungsten alloy and steel projectile l8 and four longitudinal slots 16 located apart, which receive the four full caliber projectile fins 17. The open sections of slots 16 left after insertion of the projectile fins 17 and clearance around center hole 15 are sealed by troweling in a room temperature vulcanizable rubber, e.g. silicone rubber. The projectile is provided with four full caliber quadrantal steel sabot blocks 19 and four high density, quadrantal polyethylene sabot blocks 20, which are held in place by a tightly fitting, subcaliber annular sabot band 21 of high density polyethylene or the like. Sabot elements 20 and 21 abut against the rear face of steel sabot blocks 19 attached to projectile 18 by means of buttress threads (not shown), which prevent forward movement of said blocks 19 but permit re moval thereof from the projectile by centrifugal force resulting from projectile spin and aerodynamic drag. Annular sabot band 21 is scored, perforated or otherwise treated to provide regions of weakness therein, which permit it to break up and be removed from the projectile together with the other sabot pieces by centrifugal force resulting from projectile spin as well as aerodynamic drag and thrust forces acting on domed end of casing 11. This subassembly of sabot elements 19, 20 and 21 in cross section possesses an essentially solid structure, whose rear end abuts against and con forms to the entire surface of the dome end of casing 11 and is attached thereto mechanically or by means of a suitable adhesive, e.g. mastic or an epoxy resin adhesive. Thus, the said subassembly effectively backs up and reinforces the entire front end of the casing against rupture by the propellant gases, which as a result can develop maximum reaction and acceleration of the projectile.

When the propellant charge is fired, a gas pressure of the order of about 60,000 psi, is rapidly generated within casing 11 and the combustible base cap 12 is simultaneously consumed. This allows the gas pressure within the casing to react against the breech area of the gun and the closed forward end of casing 11, which forces the casing forward and outwardly against the gun barrel and thus causes the casing to 1. provide a self-obturating function, i.e. seal the gases behind the projectile and cause the casingprojectile assembly to be expelled from the weapon, and

2. engage the barrel rifling to impart a roll" i.e. a low order of spin, e.g. 30 rps. to the casing-projectile assembly sufficient to throw off sabot elements 19, 20 and 21 and provide aeronautical stability to the projectile (e.g. freedom from yaw, etc.).

On exiting from the weapon the casing explodes into irregular pieces of chaff, which are light and separate easily from the cone of fire immediately in front of the weapon.

inspection of the gun breech after the cartridge had been fired revealed no residue or fragments requiring removal, so that it was possible to insert another cartridge into the weapon with complete safety.

In the cartridge of the present invention the purpose of the sabot assembly attached to the projectile is to provide a solid wall, which abuts and in effect supports the closed end of the propellant casing against the explosive pressure of the propellant gases so that the latter can devleop maximum reaction and acceleration of the projectile.

The closed end of the propellant casing is advantageously dome shaped but it may also be flat, etc. When a casing is employed, wherein the closed front end is flat or joins the casing wall at an angle close to 90, the joint represents a relatively weak zone; hence it is desirable to strengthen such a joint by suitable reinforcement, e.g. greater wall thickness on both sides of the joint, or filling the angle behind the joint with an epoxy or other resin which bonds to the wall and closed end of the casing structure.

The projectile illustrated in the drawing has full caliber fins, but subcaliber fins may also be employed, e.g. wherein the fins may rest on a metal insert molded in the case. With high velocity fin-stabilized projectiles of the type illustrated above, pressures of the order of 60,000 to 80,000 psi or more are usually developed in the gun. Such projectiles depend essentially on fins for flight stability but are usually imparted a roll" or low spin, e.g. 30 rps, sufficient to prevent yaw, etc. and also to remove sabot elements by centrifugal force. In contrast, spin-stabilized projectiles require a much higher order of spin (e.g. 1,000 rps and higher) and relatively low gun pressures (e.g. 30,000 psi) to achieve gyroscopic flight stability.

The cartridge casing employed in the present invention is desirably made of a flexible organic plastic, preferably having an elongation of at least about 400 percent, and especially about 500 1000 percent, such as for example a high density polyolefin, e.g. polyethylene and polypropylene. Highly malleablemetals possessing similar elongation, e.g. tin and aluminum, are also suitable. Organic plastics however generally provide advantages in cost and ease of fabrication of the casing and hence are preferred. Casings fabricated of rigid or brittle plastic, such as polyacetal resin, tend to fracture under such high gun pressures and explosive shock and leave fragments behind, whereas a casing of flexible material like polyethylene travels through the gun barrel essentially intact and is completely expelled.

The sabot elements can be made of materials conventionally used for the purpose, e.g. high density polypropylene and polyethylene, similar to that employed in the casing.

The ventable base cap of the cartridge casing can be of a combustible type, e.g. a conventional molded nitrocellulose-Kraft fiber-resin mixture which is consumed under the firing conditions; or it may be a nonconsumable organic plastic or metal plate containing holes through which the propellant gases can be vented so that the pressure thereof is not applied against the base cap but rather is applied to the breech area to expel the cartridge. To contain and protect the propellant charge in the casing prior to firing, the holes are covered with a suitable material, e.g. thin plastic sheet, which will fail before the closure cap on firing of the propellant.

it is thus evident that the novel cartridge of the present invention represents a significant technical advance in the art, providing the following advantages:

1. the non-consumable casing is completely expelled along with the projectile leaving no dangerous residue in the weapon;

2. the obturating function is assumed by the casing, thereby eliminating the costly and complex obturating band installation, which in the previous design was required to move forward under the gun pressure to seal the gases behind the projectile;

3. the casing is fabricated of organic plastic material, such as polyethylene, which is strong, non-flammable, unaffected by moisture, oils, etc. and capable of with standing normal handling.

We wish it to be understood that we do not desire to be limited to the exact method and detail of construction described for obvious modification will occur to persons skilled in the art.

What is claimed is:

.1. A cartridge comprising in combination:

an elongated projectile body having a forward end and a rearward end and fins extending radially from said body at said rear end thereof;

a non-consumable, flexible, tubular cartridge casing having a vented closure at one end and a front end closure at the other end, said front end closure initially defining a central aperture, the elongated projectile body received through said central aperture, the forward end of said projectile body being external to said casing and projecting beyond the front end closure thereof;

annular sabot means mounted on the forward end of said projectile body and having one end abutting against said front end closure, said sabot means capable of being removed from said projectile body by centrifugal and aerodynamic forces; and

a propellant charge within said casing;

said casing vented closure permitting exit of gases therefrom upon initiation of said propellant, whereby the tubular casing provides a selfobturating function in a weapon barrel and separates from said projectile on exit therefrom.

2. A cartridge according to claim 1, wherein said casing is made of an organic plastic having an elongation of at least about 400 percent.

3. A cartridge according to claim 2, wherein the organic plastic is a polyolefine of the group consisting of 5 polyethylene and polypropylene.

4. A cartridge according to claim 9, wherein the ventable closure is composed of combustible material which is consumed on firing.

5. A cartridge according to claim 9, wherein the front end of said casing is attached to the abutting end of said sealing said radial slots. 

1. A cartridge comprising in combination: an elongated projectile body having a forward end and a rearward end and fins extending radially from said body at said rear end thereof; a non-consumable, flexible, tubular cartridge casing having a vented closure at one end and a front end closure at the other end, said front end closure initially defining a central aperture, the elongated projectile body received through said central aperture, the forward end of said projectile body being external to said casing and projecting beyond the front end closure thereof; annular sabot means mounted on the forward end of said projectile body and having one end abutting against said front end closure, said sabot means capable of being removed from said projectile body by centrifugal and aerodynamic forces; and a propellant charge within said casing; said casing vented closure permitting exit of gases therefrom upon initiation of said propellant, whereby the tubular casing provides a self-obturating function in a weapon barrel and separates from said projectile on exit therefrom.
 2. A cartridge according to claim 1, wherein said casing is made of an organic plastic having an elongation of at least about 400 percent.
 3. A cartridge according to claim 2, wherein the organic plastic is a polyolefine of the group consisting of polyethylene and polypropylene.
 4. A cartridge according to claim 9, wherein the ventable closure is composed of combustible material which is consumed on firing.
 5. A cartridge according to claim 9, wherein the front end of said casing is attached to the abutting end of said sabot means with an adhesive.
 6. A cartridge according to claim 1, wherein the projectile has full caliber fins and said front end closure initially contains radial slots extending from said aperture, the elongated projectile body and fins received within said casing through said central aperture and said radial slots, respectively.
 7. A cartridge according to claim 6 having means for sealing said radial slots. 